Tim, would you show us more of your WTC? What is unconventional about it? Photos?
I forgot to say how cool it looks in the water. Great job there!

Tom,

the ballast tank pump is built from thunder tiger neptune spare parts, a brushless motor, brushless esc, with basic receiver failsafe setup thrown in for safety. it fills or empties a bladder with water, and it appears i guessed the right speed brushless motor, the bladder is filled and emptied at a reasonable speed.

photos soon. right now i am busy getting the rest of the subs ready for next week.

just a quick update, the skipjack had its maiden voyage today at the Colorado Crew regatta, got video and pictures of it running on the surface, and submerged. I also took a bunch of photos of its WTC, i will be uploading them here on monday. the maiden voyage went great, only problem was the throttle setting needs to be dialed back to about half of what it currently is, max speed is about a scale 80 knots. ran it for 30 minutes with no leaks.

Images

basically what i have done is taken some major replacement parts from the thunder tiger neptune and adapted them to work for me. by buying these replacement parts i was able to save a ton of money versus buying from the germans.

the moebius sub kit itself retails for around $90.00, i bought mine from freetime hobbies. I also bought the g-factor brass prop from them:http://www.freetimehobbies.com/GFM17204/ it took a lot of finesse to get the prop and prop shaft aligned nicely, i ended up using JB Weld to bond the prop to the propshaft, after machining the shaft to fit the prop.

i bought a 4mm propshaft and stuffing tube from cornwall model boats, not sure which length, but the stuffing tube is about 5"... maybe $10 plus shipping.

by getting the programmer, i am able to set the max speed of the motor to a more reasonable 6000 rpm at the prop, rather than the 15000 that the motor/esc/battery combo actually produces.
subtotal of parts: $60

then the thundertiger neptune motor mount/shaft seal, as well as the shaft, and u-joint:

the pump esc is the most expensive individual part, and i had it sitting in my parts box, otherwise i would have tried a 1/18 esc from hobbypartz or hobbyking, something to look into later, the ESC is overkill for the specific situation.

Tim,
Great information and photos & video. Thank you for posting.
Would you repost the ESC link?, it is the same as the pump motor. And what features in the Sombra Labs RX did you use? would you elaborate?

the basic functionality of the sombra labs receiver allows me to set the failsafe position for the pump esc so that the bladder is emptied when the receiver loses signal (Program Value 96). this isn't as nice as the brushed pump controllers that norbert and engel sell, they also have low battery and pressure failsafes as well, but for 90% of the failure scenarios, the simple signal failure is enough. this receiver programming mode allows all 8 channels to be set to a user defined value, so along with the pump being set to "empty", all other channels are set to equally useful values (neutral dive planes and rudder, no throttle)

1) sensored hobbyking ESC for the main motor, programmed with the programming box to give it max forward and reverse speed of 40% of original max speed (roughly 6000rpm), as small a deadband/neutral range as possible, low startup speed, and very low motor timing. basically setting it up opposite to how it would be setup for a fast car.
the sensored setup is how i am able to get such nice slow speed capabilities. max throttle is a little over scale, giving me a "panic" get out of harms way capability.

2) castle sidewinder micro ESC, used for the pump motor, and the only programming i have done for it is to give it zero brake, zero delay and 100% forward and reverse so when dealing with the pump, fill and empty take the same time. like i said, the castle esc is way over kill for what it is doing, but it was sitting on the shelf. programming was done with a castle link.